Rocuronium Dosing by Total Body Weight Prolongs Duration of Action

When rocuronium is dosed by actual body weight in nonobese patients, is its duration of action associated with body-mass index (BMI)? To find out, researchers studied 16 healthy Japanese women aged 45 to 60 with BMI 15–30 kg/m² who were undergoing elective abdominal or lower extremity surgery. Patients received a single dose of rocuronium administered at 0.9 kg/m². Times to 5% and 25% recovery of train-of-four response were calculated to determine duration of neuromuscular blockade. Patients on antibiotics and anticonvulsants were excluded.

Overall, the mean 5% and 25% durations of action increased with increasing BMI: 42 and 57 minutes in patients with low BMI (15–20), 41 and 49 minutes for those with normal BMI (20–25), and 63 and 83 minut…